Mixing column for medical humidifier and method of humidifying inhalable gases

ABSTRACT

A multi-stage sieve plate humidifier column with a series of plastic snap together modular mixing units that combine to form an elongated vertical column with interconnected mixing chambers. The column is confined inside a liquid supply bottle where it is submerged in a liquid used to humidify an inhalable gas such as oxygen or air. In a method of humidification, the gas is bubbled into a lower portion of the submerged column, transferred through the interconnecting chambers of the column where the bubbles are broken up and mixed with liquid, and then the humidified gas collected near a top of the column and conducted to a patient for inhalation.

ii I

atent [75] Inventor: Charles .1. MePhee, Sylmar, Calif. [73] Assignee: American Hospital Supply Corporation, Evanston, Ill. [22] Filed: June 19, 1972 [21] Appl. No: 264,314

[52] 11.3. C1 261/123, 128/188, 128/194, 261/DIG. 65 [51] int. C1. 1801i 3/04, A61m 15/00 [58] Field of Search 128/186-188, 128/194; 261/122-123, 114 R, DIG. 65

[56] References Cited UNITED STATES PATENTS 676,713 6/1901 Cross 128/186 X 1,064,535 6/1913 Pindstofte.... 261/122 X 1,165,281 12/1915 Paulson 261/114 R X 2,672,330 3/1954 Swenson 261/114 R X 3,429,676 2/1969 Gatza 261/123 X 3,572,660 3/1971 Mahon et a1 261/78 A 11] 3,834,682 Sept. 10, 1974 FOREIGN PATENTS 0R APPLICATIONS 48,277 8/1889 Germany 261/123 Primary Examiner-Tim R. Miles Assistant Examiner-Richard L. Chiesa Attorney, Agent, or Firm-Larry N. Barger; Robert T. Merrick [57] ABSTRACT A multi-stage sieve plate humidifier column with a series of plastic snap together modular mixing units that combine to form an elongated vertical column with interconnected mixing chambers. The column is confined inside a liquid supply bottle where it is submerged in a liquid used to humidlify an inhalable gas such as oxygen or air. In a method of humidification, the gas is bubbled into a lower portion of the submerged column, transferred through the interconnecting chambers of the column where the bubbles are broken up and mixed with liquid, and then the humidified gas collected near a top of the column and conducted to a patient for inhalation.

32 Claims, 6 Drawing Figures PATENTEDSEP101974 3.834.682 I Ii y //y/ I L- 1 MIXING COLUMN FOR MEDICAL IIUMIDIFIER AND METHOD OF HUMIDIFYING INHALAIBLE GASES BACKGROUND In recent years inhalation therapy has been used very extensively for treatment of emphysema and other lung and respiratory diseases, as well as postoperative treatment and cardiac patient care. One form of inhalation therapy involves mixing a breathable gas such as air or oxygen with a liquid. This humidified gas is supplied to' a mask, nasal cannula, or tent where it is breathed by the patient and absorbed by his lungs. A conventional medical humidifier system includes a dry gas source such as a portable oxygen tank or central oxygen supply system of a hospital, coupled with a container of humidifying liquid. Humidification in the past has been accomplished by atomizing the liquid into the gas or simply bubbling the gas into the liquid from an end of a submerged tube. Sometimes the end of the tube would have a porous gas diffusing covering.

There have been several problems in the past with these gas-liquid mixing humidifiers. One of the problems was the limit of absorbed liquid carried by the gas to the patient for breathing. Often a physician desired to have very high relative humidity of the humidified gases inhaled. This is so that the nasal and other membranes would not dry out. The previous humidifiers produced humidified gas roughly in the range of 60 to 75 percent relative humidity. A physician sometimes desires relative humidities at 80 percent or more.

In previous humidifiers there was also a problem of an unpleasant gurgling or churning noise as the gas was bubbled into the liquid. Over prolonged periods of time such as several days or a week that a patient received inhalation therapy this noise sometimes became very annoying. 1

SUMMARY OF THE INVENTION I have overcome the problems of the previous medical humidifiersfor inhalation therapy by providing a multi-stage stacked sieve plate column submerged in the liquid supply bottle. This column includes a series of vertically spaced sieve plates that divide thecolumn into a series of separate chambers. In a method of humidifying gas, the dry gas is bubbled into a lower portion of the submerged column and mixes with liquid in each chamber as the gas is transferred upwardly from one chamber to the next. At a top of the submerged column the humidified gas is collected at very high relative humidities of approximately 82 percent and then conducted to a patient for breathing.

The submerged mixing column with its series of stacked sieve plates repeatedly break up the gas bubbles into small bubbles to provide large gas-liquid innerface surface area for molecular transfer during the humidifying process. This submerged mixing column has a unique construction in that it is formed of a series of modular snap together thermoplastic units. The column formed in this way is sufficiently inexpensive so as to be confined in and become a permanent part of a liquid supply bottle. Once the contents of the bottle have been consumed to a desired level, the entire bottle, multi-stage mixing column, etc., are discarded. This reduces the risk of cross-contamination between patients.

The submerged stacked humidifier column with its multiple sieve plates also acts as a muffler to quiet the humidifying process. Instead of a loud gurgling noise,

THE DRAWINGS FIG. 1 is a front elevational view partially in section showing the submerged modular humidifier column in the liquid supply bottle;

FIG. 2 is an enlarged sectional view of the lower three mixing chambers of the submerged humidifier column;

FIG. 3 is a further enlarged sectional view of anindividual snap-together modular unit of the humidifier column;

FIG. 4 is an enlarged sectional view of a bottom cap that snaps to the humidifier column;

FIG. 5 is a cross sectional view taken along line 55 of FIG. 3; and

FIG. 6 is a sectional view taken along line 66 of FIG. 1.

DETAILED DESCRIPTION Referring to these drawings, FIG. 1 shows the medical humidifier system connected for administering humidified gas to a patient. The system includes a dry gas source 1 shown schematically in the form of a threaded nipple from an oxygen tank or oxygen wall supply line of a hospital. Connected to this dry gas source is a dual passage adapter 2 which is explained in more detail in my co-pending application entitled Port System for Medical Humidifier Container filed June 9, 1972, Ser. No. 264,315. This adapter 2 is permanently connected at the time of use to a cap 3 of a liquid supply bottle 4 and this cap is in turn permanently connected to bottle 4. Thus, adapter 2 can reliably support the bottle 4 from its cap 3 when the bottle is suspended from dry gas source 1 as shown in FIG. 1.

Inside bottle 4 is a liquid 5 and a submerged humidifier column 6. It is to this submerged humidifier column that the present invention pertains. As shown in FIG. 1 the column is divided into a series of separate compartments numbered from 7 through 12. A compartment at a top of the humidifier column indicated at 13 is connected to a special defoamer housing 14. This defoamer housing 14 separates out humidified gases ready for transfer to a patient and recycles large water drops and foam to the liquid 5. This defoamer chamber is explained in more detail in my co-pending application entitled Defoaming Device for Medical Humidifier" filed June 19, 1972, Ser. No. 264,350, and now US. Pat. No. 3,793,810.

In operation, the FIG. 1 humidifier arrangement has a dry gas source I that feeds into a dry gas tube 15. This dry gas tube 15 has an outlet 16 adjacent a bottom of the liquid filled container. Throughout this specification the term dry gas" is used to distinguish oxygen air, etc., before it becomes humidified in the mixing column. As seen in FIG. 1, this dry gas tube 15 extends through a center axial portion of the stacked vertical column. Liquid from the bottle enters through a series of passages in a bottom cap portion 17 to at least partially fill the chambers 7 through 12. The number of chambers filled depends on the level of liquid in bottle 4. To insure that a sufficient portion of the humidifier column is always submerged for properhumidification an indented portion 55 indicates that the bottle should be replaced when the liquid in the bottle has been consumed down to this level.

During the humidification process, the dry gas is bubbled up through a series of transverse sieve plates in the submerged column, illustrated as l8, 19, and 21. Each of these sieve plates has a series of holes for breaking up the large bubbles and muffling the mixing noise. The details of the modular sieve plate units will be explained in more detail with reference to subsequent drawings.

The submerged multi-chambered humidifier column explained above is better shown in the'more enlarged view of FIG. 2. Here, as briefly explained before, the dry gas from a dry gas source 1 is fed through a dry gas column 15. As the dry gas exits through bottom end 16 of dry gas tube, the bubbles move upwardly through the liquid 5 in the lowermost chamber 7. This causes the molecular liquid to diffuse across the liquid-gas interface of the bubble wall. The dry gas thus takes on a higher humidity as expressed in FIG. 2 as H,. The humidified gas then proceeds upwardly in the column through a porous sieve plate 18. Sieve plate 18 has a series of holes that break up the large air bubbles that tend to form in an air pocket portion 22 of chamber 7. Breaking up the bubbles in this way creates a very large number of small bubbles that have a greater surface area of the liquid-gas interface. This causes improved mixing and the gas picks up a higher humidity in chamber 8 as illustrated by H This process is repeated as the gas proceeds upwardly through the several stacked vertical chambers separated by sieve plates.

An advantage of breaking up the bubbles with a series of sieve plates rather than with a porous covering over a single outlet of a submerged tube is that the sieve plate bubbles have a very short half life and cause considerably less foaming in a liquid containing a bacteriastat, such as a paraben.

At an upper area of the bottle, the humidified gas is collected and passes through a passage 25 where it is thereafter conducted through a tube 26 leading to a patient. The patient can thus breathe the humidified gas with a very high relative humidity during inhalation therapy. The previous medical humidifiers used essentially a one stage humidifying process by using the entire bottle contents as a mixing chamber. One process bubbled dry as into the liquid bottle. Another process used an atomizer inside the bottle. These previous humidifiers would gt the relative humidity to be approximately 60 to 75 percent when it was administered to a patient. The applicants improved humidifier system can deliver humidified gas at relative humidities of approximately 82 percent. By more closely approximating the relative humidity of the respiratory tract, the patient suffers less drying of the mucous membrane.

The improved modular mixing column with the sieve plates shown in FIG. 2 also provide a very important advantage over previous one stage humidifiers. The atomizing type humidifiers create an annoying wheezing sound. The single chamber bubble type humidifiers cause an annoying gurgling or churning sound as the bubbles were free to migrate unbroken from the bottom of the container to atop liquid surface. Such unrestricted bubbles tended to cling together and burst into large bubbles as they moved upwardly to cause a splashing and churning at a top surface of the liquid 5 when they broke through the liquid surface. Over long periods of time this caused a very annoying sound to the patient and the attending physicians and nurses.

With my improved multi-stage humidifier column, these bubbles are rebroken into small bubbles at each transfer across the sieve plates. After the bottle had been filled with liquid, but before the dry gas tube has been turned on, the level in the bottle, and the level within the column are the same. All chambers below the liquid level are completely filled with liquid, and all chambers above the liquid level are empty.

When the dry gas tube is supplied with pressurized dry gas as illustrated in FIGS. 1 and 2, this increases the pressure in the chambers and forces some of the liquid out of each chamber. This displaced liquid takes the course of least resistance, and the increased pressure exerted from the bottom of the column causes the displaced liquid to move to a chamber above. Although the liquid in the humidifier is not at a boiling temperature as in a coffee percolator, it visually appears to act somewhat like a coffee percolator in moving liquid up the column above the liquid level in the bottle. Additionally, turbulence of the gas above the liquid level in each chamber is believed to cause some entrainment of the liquid with the gas as the gas move to a higher chamber. Also, contributing to this upward movement of liquid is the small size of ports in the sieves. The sieves have openings of approximately 0.093 inch diameter, and these small openings allow only slow downward draining of the liquid subject to pressure therebeneath; the bubbles, of course, pass through liquid accumulated in the stacked chambers.

After pressure in the dry gas tube has been turned off, substantially all of the liquid in the column will settle to the approximate level as the liquid in the bottle, with all chambers below the liquid level being substantially entirely filled with liquid, and all chambers above the liquid level will substantially empty. This function of the mixing column provides a mixing column with an effective liquid length for mixing that is not limited by its submerged length or the depth of liquid in the bottle. This causes a very definite muffling action of the mixing within the chambers. Also the chambers are confined in a tubular mixing column located in the center portion of the bottle. The surrounding liquid 5 also acts as a sound deadening barrier between the mixing column and an outer wall of the bottle 4.

Having discussed the complete multi-chambered column and how it works above, the individual modular units of the column will now be discussed. An individual modular unit 30 is shown in further enlarged sectional view of FIG. 3. This unit 30 is shown in FIGS. 1 and 2 as defining the chamber 7. This modular unit 30 includes a tubular outer wall 31 that has an upstanding flange 32 at its upper end and a downwardly extending flange 33 at its lower end. These respective flanges include a groove 34- on an outer surface of flange 32 and an annular rib 35 on an inner surface of lower flange 33. These two flanges also have respective tapered lead-in surfaces 36 and 37. These flange structures are formed so that a series of identical modular units such as 30 can be snapped together into a vertical stacked column as shown in FIG. 2. The top flange 32 of one modular unit mates a lower flange of a modular unit directly above.

Each modular unit includes a sieve plate 18 which is integral with tubular wall 31 and extends transversely across the chamber 7 of the modular unit. The sieve plate includes a series of holes illustrated as 39 and 40 and the arrangement of these holes which break up the large bubbles of gas is shown in more detail in FIG. 5.

Integral with the sieve plate and concentrically disposed on a common longitudinal axis with a cylindrical outer wall 311 is a dry gas tube segment 41. This dry gas tube segment includes an integral sleeve portion d2 adjacent its upper end. This sleeve portion 42 has a receiving surface 43 that extends between a tapered leadin surface &4 and a stop shoulder 45. A lower end of the dry gas tube segment includes an external tapered leadin surface 46. Thus when a series of modular units 30 are snapped together to form the vertical stacked humidifier column, the dry gas tube segments will interfit to create the elongated dry gas column or tube 115 with a generally constant internal diameter that extends from a top portion of the medical liquid bottle to a bottom portion I6. The dry gas tube segment 41 is on a common longitudinal axis with outer tube wall 31. Thus, when the modular units are snapped together there need be no angular rotational orientation of the parts to get them to fit together.

At a bottom of the multi-chambered mixing column is a bottom cap 50. This bottom cap has an upstanding flange 51 of similar construction to upstanding flange 32. A transverse bottom wall 52 of the bottom cap includes a series of holes 53 and 54. This bottom cap 50 snaps into the bottom end of the lowermost modular mixing unit to form the bottom mixing chamber. Liquid 5 from the bottle enters the multi-stage mixing humidifier column through holes such as 53 ad 54.

FIG. 5 shows the arrangement of the holes in sieve plate 110. Here, atypical arrangement in the sieve plate includes two rings of holes with each hole being from 0.070 to 0.120 inch diameter. I have found holes in this range 0.093 inch diameter for example, are very effective in breaking up the large air bubbles while still providing sufficient opening for gas and liquid transfer across the sieve plates. The hole arrangement in the bottom cap is shown in FIG. 6. Four holes such as 53 and 54 in bottom wall 52 are sufficient to supply the column with liquid. These holes are from 0.070 inch to 0.120 inch diameter.

The modular mixing units and bottom cap 50, I have found, snap together very effectively and form a sturdy vertical column when injection molded of a thermoplastic material such as polypropylene. The injection molded modular unit of the humidifier column permit it to be made sufficiently inexpensive so it can be discarded after a single use.

In the above description of my invention, I have used specific embodiments to describe my invention. However, it is understood by those skilled in the art that modifications can be made to these embodiments without department from the spirit and scope of the inven tion.

I claim:

I. In an inhalation therapy system for administering a humidified gas to a patient, an inhalation therapy humidifer comprising in combination:

a disposable container including an outer wall for defining a liquid-containing reservoir;

a liquid at least partially filling said container reservoir;

a tubular multi-stage mixing column for containing gas therein fitting within container and spaced from said container wall and having a lower portion submerged in and communicating with said liquid, said column having means defining a plurality of series-interconnected gas-liquid mixing chamber for progressively humidifying the inhalation gas with the liquid as the gas ascends through the series of interconnecting mixing chambers in said column, said chambers being separated by a transverse partition common to adjacent chambers having a plurality of holes connecting adjacent chambers for breaking up inhalation gas into bubbles in the column to increase the gas-liquid interface, the chamber having tubular walls connected to and extending between said partitions and defining an independent conduit opening into the lower portion of said column, and communicating with said liquid in the column; said humidifier having a humidifiedgas outlet communicating with the uppermost chamber for directing humidified gas to a patient being treated.

2. The combination as set forth in claim 1 wherein the humidifier is disposable and the mixing column is permanently connected to the container so the mixing column cannot be used with more than one container.

3. The combination as set forth in claim 1 wherein the mixing chambers are vertically stacked units one upon another and form an elongated vertical column, the lowermost portion of which column is submerged in said liquid.

4. The combination as set forth in claim 3 wherein said conduit includes means for connecting a pressurized dry gas supply source with a lowermost chamber of the column.

5. The combination as set forth in claim 4 wherein the dry gas feed tube is disposed within said vertical column.

6. An inhalation therapy humidifier comprising in combination: a container; a liquid at least partially filling said container; a multi-stage mixing column fitting within said container and having a portion submerged in said liquid, said column having a plurality of interconnected gas-liquid mixing chambers for humidifying the gas with the liquid as the gas passes through the interconnecting mixing chambers, each gas-liquid mixing chamber comprising a transverse sieve plate floor and a vertical tubular wall member connected to said sieve plate, each sieve plate and tubular wall member forming a modular mixing unit connected in vertically stacked relationship to similar units to form the multistage mixing column of the humidifier.

7. The combination as set forth in claim 6 wherein the sieve plate of each module has a dry gas feed tube protruding through the sieve plate.

8. The combination as set forth in claim 6 wherein each modular gas-liquid mixing chamber has snap fit connecting means for attaching to a similar mixing unit.

9. The combination as set forth in claim 8 wherein the snap fit means includes an annular rib adjacent one end of the mixing unit and an annular groove adjacent an opposite end of the unit.

10. The combination as set forth in claim 6 wherein there is a perforate cap member attached to the lowermost mixing chamber, said cap member being submerged in said liquid and having openings therethrough causing liquid to flow upwardly into said column.

11. In a humidifier column the improvement of a modular mixing unit comprising a sieve plate; a tubular wall member connected to said sieve plate; and a dry gas feed tube attached to said unit formed by the tubular wall and sieve plate, said dry gas feed tube extending from an upper end to a lower end of the mixing unit; said unit having attachment means adjacent its upper end and adjacent its lower end; whereby a plurality of said mixing units can be vertically stacked and connected together at their attaching means to provide a multi-stage mixing column for liquid and gas.

12. The combination as set forth in claim 11 wherein the tubular wall extends below sad sieve plate.

13. The combination as set forth in claim 11 wherein the tubular wall is cylindrical and has a central vertical longitudinal axis and the dry gas feed tube is co-axial with and concentrically disposed within the tubular wall, whereby modular mixing units can be connected together without rotationally orienting one relative to the other.

14. The combination as set forth in claim 11 wherein the sieve plate has a series of holes therethrough each with a diameter of 0.070 to 0.120 inches.

15. The combination as set forth in claim 11 wherein the dry gas feed tube has connecting means at one end for receiving a dry gas tube of an adjacent modular mixing unit.

16. The combination as set forth in claim 15 wherein the dry gas tube connecting means includes an enlarged receiving sleeve connected with the sieve plate and this sleeve has an inwardly tapered lip surface, an internal annular receiving surface inside the sleeve having a diameter larger than the internal diameter of the gas tube, and a shoulder surface laterally extending from the annular receiving surface tothe dry gas tubes internal receiving surface; whereby the dry gas tubes of a series of modular mixing units fit together and provide an elongated dry gas feed line with a generally constant internal diameter.

17. The combination as set forth in claim 11 wherein the modular mixing unit has an upstanding annular flange above said sieve plate for connecting to a tubular wall member of a modular mixing unit immediately thereabove.

18. The combination as set forth in claim 17 wherein the modular mixing unit has an upstanding annular flange has retention means thereon for forming a snap fit with the tubular wall of the mixing unit immediately thereabove.

19. The combination as set forth in claim 18 wherein the modular mixing unit includes a retention means adjacent a lower portion of its tubular wall for snap fitting with a retention means on an upstanding annular skirt of a modular mixing unit immediately therebelow.

20. The combination as set forth in claim 19 wherein the snap fit means includes a mating rib and groove structure for holding together adjacent modular mixing unit.

2]. In an inhalation therapy system, a multi-stage mixing column for a disposable medical gas humidifier including a bottle with an outer wall forming a reservoir; a liquid at least partially filling said bottle a tubular column vertically depending into said bottle, spaced from said wall and having at least a lower portion thereof submerged in and communicating with said liquid; a series of vertically spaced, transverse perforated plates extending across and disposed within said column and defining series-connected chambers; a vertical dry gas tubular feed line of smaller cross sectional passage area than the mixing column axially disposed within said mixing column and extending through said perforated plates, so as to feed isolated pressurized dry gas axially from a top portion of the column through the various perforated plates to a bottom chamber of the column; connector means for attaching said dry gas feed line to a pressurized dry gas supply source; and connecting means for attaching an upper portion of the mixing column with a conduit for channeling humidifled gas from a top of the mixing column to a patient for inhalation therapy, said perforated plates being constructed and arranged to retain liquid thereabove and above the level of liquid in said bottle reservoir.

22. The combination as set forth in claim 21 wherein the mixing column includes a bottom cap having at least one opening therethrough for passage of liquid into the column from within the bottle and surrounding the lowermost chamber of the mixing column.

23. The combination as set forth in claim 22 wherein the dry gas feed line has a bottom exit port adjacent and above said bottom cap so dry gas can be fed into an area within the bottom cap and mixed with liquid and humidified as the gas ascends through the vertical mixing column exteriorly of said tubular feed line.

24. The combination as set forth in claim 21 wherein the column is spaced from the container wall along its submerged portion so the liquid in the reservoir and column muffles the mixing of gas and liquid in the column.

25. A modular unit for constructing a multi-stage mixing column for liquid and gas comprising: a one piece integrally molded thermoplastic unit including a tubular housing wall and a transverse porous sieve plate extending across the housing wall; an internal dry gas tube formed with the sieve plate and housing wall; said housing wall and dry gas tube each including coupling means at their opposite ends for joining the unit to a similar one piece modular unit to form an elongated multi-compartment mixing column.

26. The combination as set forth in claim 25 wherein the tubular housing wall includes a rib and groove construction for snap fitting two or more modular units together.

27. The combination as set forth in claim 25 wherein the tubular housing wall has an upstanding annular flange adjacent its upper end which flange has an annular beveled wedge surface thereon.

28. The combination as set forth in claim 25 wherein the tubular housing wall includes a depending annular flange adjacent its lower end with a beveled wedge surface thereon.

29. The combination as set forth in claim 25 wherein the dry gas tube is integrally formed with the sieve plate and centrally located thereon so as to have a common longitudinal axis with the tubular housing wall.

30. The combination as set forth in claim 25 wherein the gas tube includes a coupling member at an upper end, and said coupling member includes an enlarged receiver sleeve with an inwardly tapered upper lip surface, a transverse shoulder surface below said lip surface and an inner wall surface between the lip surface and shoulder surface; and said dry gas tube has a lower coupling portion that includes a tapered end surface adapted to engage the tapered lip surface of a dry gas tube receiving sleeve of an adjacent similar modular unit, whereby the modular units can be coupled to form a continuous dry gas feed line extending through a plurality of modular mixing units.

31. A method of humidifying a medical gas for direct administration to a patient during inhalation therapy comprising the steps of:

forcing pressurized dr'y medical gas confined axially and downwardly into a lower reservoir portion of a container at least partially filled with a humidifying liquid;

restricting the gas axially and directing it progressively upwardly through a series of vertically stacked interconnecting chambers with a portion of the chambers being submerged in said liquid and portion of the chambers extending above the liquid before it ascends through the liquid above the' plates and at a substantially reduced noise level; collecting the gas most highly humidified adjacent the top of the container; and conducting the humidified gas into a feed line adapted to be'connected to a patient for breathing.

32. The method as set forth in claim 31 including progressively directing the gas through at least three humidifying chambers as it proceeds from a lower portion of the container to an upper portion of the container. 

1. In an inhalation therapy system for administering a humidified gas to a patient, an inhalation therapy humidifer comprising in combination: a disposable container including an outer wall for defining a liquid-containing reservoir; a liquid at least partially filling said container reservoir; a tubular multi-stage mixing column for containing gas therein fitting within container and spaced from said container wall and having a lower portion submerged in and communicating with said liquid, said column having means defining a plurality of series-interconnected gas-liquid mixing chamber for progressively humidifying the inhalation gas with the liquid as the gas ascends through the series of interconnecting mixing chambers in said column, said chambers being separated by a transverse partition common to adjacent chambers having a plurality of holes connecting adjacent chambers for breaking up inhalation gas into bubbles in the column to increase the gasliquid interface, the chamber having tubular walls connected to and extending between said partitions and defining an independent conduit opening into the lower portion of said column, and communicating with said liquid in the column; said humidifier having a humidified-gas outlet communicating with the uppermost chamber for directing humidified gas to a patient being treated.
 2. The combination as set forth in claim 1 wherein the humidifier is disposable and the mixing column is permanently connected to the container so the mixing column cannot be used with more than one container.
 3. The combination as set forth in claim 1 wherein the mixing chambers are vertically stacked units one upon another and form an elongated vertical column, the lowermost portIon of which column is submerged in said liquid.
 4. The combination as set forth in claim 3 wherein said conduit includes means for connecting a pressurized dry gas supply source with a lowermost chamber of the column.
 5. The combination as set forth in claim 4 wherein the dry gas feed tube is disposed within said vertical column.
 6. An inhalation therapy humidifier comprising in combination: a container; a liquid at least partially filling said container; a multi-stage mixing column fitting within said container and having a portion submerged in said liquid, said column having a plurality of interconnected gas-liquid mixing chambers for humidifying the gas with the liquid as the gas passes through the interconnecting mixing chambers, each gas-liquid mixing chamber comprising a transverse sieve plate floor and a vertical tubular wall member connected to said sieve plate, each sieve plate and tubular wall member forming a modular mixing unit connected in vertically stacked relationship to similar units to form the multi-stage mixing column of the humidifier.
 7. The combination as set forth in claim 6 wherein the sieve plate of each module has a dry gas feed tube protruding through the sieve plate.
 8. The combination as set forth in claim 6 wherein each modular gas-liquid mixing chamber has snap fit connecting means for attaching to a similar mixing unit.
 9. The combination as set forth in claim 8 wherein the snap fit means includes an annular rib adjacent one end of the mixing unit and an annular groove adjacent an opposite end of the unit.
 10. The combination as set forth in claim 6 wherein there is a perforate cap member attached to the lowermost mixing chamber, said cap member being submerged in said liquid and having openings therethrough causing liquid to flow upwardly into said column.
 11. In a humidifier column the improvement of a modular mixing unit comprising a sieve plate; a tubular wall member connected to said sieve plate; and a dry gas feed tube attached to said unit formed by the tubular wall and sieve plate, said dry gas feed tube extending from an upper end to a lower end of the mixing unit; said unit having attachment means adjacent its upper end and adjacent its lower end; whereby a plurality of said mixing units can be vertically stacked and connected together at their attaching means to provide a multi-stage mixing column for liquid and gas.
 12. The combination as set forth in claim 11 wherein the tubular wall extends below sad sieve plate.
 13. The combination as set forth in claim 11 wherein the tubular wall is cylindrical and has a central vertical longitudinal axis and the dry gas feed tube is co-axial with and concentrically disposed within the tubular wall, whereby modular mixing units can be connected together without rotationally orienting one relative to the other.
 14. The combination as set forth in claim 11 wherein the sieve plate has a series of holes therethrough each with a diameter of 0.070 to 0.120 inches.
 15. The combination as set forth in claim 11 wherein the dry gas feed tube has connecting means at one end for receiving a dry gas tube of an adjacent modular mixing unit.
 16. The combination as set forth in claim 15 wherein the dry gas tube connecting means includes an enlarged receiving sleeve connected with the sieve plate and this sleeve has an inwardly tapered lip surface, an internal annular receiving surface inside the sleeve having a diameter larger than the internal diameter of the gas tube, and a shoulder surface laterally extending from the annular receiving surface tothe dry gas tube''s internal receiving surface; whereby the dry gas tubes of a series of modular mixing units fit together and provide an elongated dry gas feed line with a generally constant internal diameter.
 17. The combination as set forth in claim 11 wherein the modular mixing unit has an upstanding annular flange above said sieve plate for connecting to a tubular wall member of a modular mixing unit immeDiately thereabove.
 18. The combination as set forth in claim 17 wherein the modular mixing unit has an upstanding annular flange has retention means thereon for forming a snap fit with the tubular wall of the mixing unit immediately thereabove.
 19. The combination as set forth in claim 18 wherein the modular mixing unit includes a retention means adjacent a lower portion of its tubular wall for snap fitting with a retention means on an upstanding annular skirt of a modular mixing unit immediately therebelow.
 20. The combination as set forth in claim 19 wherein the snap fit means includes a mating rib and groove structure for holding together adjacent modular mixing unit.
 21. In an inhalation therapy system, a multi-stage mixing column for a disposable medical gas humidifier including a bottle with an outer wall forming a reservoir; a liquid at least partially filling said bottle a tubular column vertically depending into said bottle, spaced from said wall and having at least a lower portion thereof submerged in and communicating with said liquid; a series of vertically spaced, transverse perforated plates extending across and disposed within said column and defining series-connected chambers; a vertical dry gas tubular feed line of smaller cross sectional passage area than the mixing column axially disposed within said mixing column and extending through said perforated plates, so as to feed isolated pressurized dry gas axially from a top portion of the column through the various perforated plates to a bottom chamber of the column; connector means for attaching said dry gas feed line to a pressurized dry gas supply source; and connecting means for attaching an upper portion of the mixing column with a conduit for channeling humidified gas from a top of the mixing column to a patient for inhalation therapy, said perforated plates being constructed and arranged to retain liquid thereabove and above the level of liquid in said bottle reservoir.
 22. The combination as set forth in claim 21 wherein the mixing column includes a bottom cap having at least one opening therethrough for passage of liquid into the column from within the bottle and surrounding the lowermost chamber of the mixing column.
 23. The combination as set forth in claim 22 wherein the dry gas feed line has a bottom exit port adjacent and above said bottom cap so dry gas can be fed into an area within the bottom cap and mixed with liquid and humidified as the gas ascends through the vertical mixing column exteriorly of said tubular feed line.
 24. The combination as set forth in claim 21 wherein the column is spaced from the container wall along its submerged portion so the liquid in the reservoir and column muffles the mixing of gas and liquid in the column.
 25. A modular unit for constructing a multi-stage mixing column for liquid and gas comprising: a one piece integrally molded thermoplastic unit including a tubular housing wall and a transverse porous sieve plate extending across the housing wall; an internal dry gas tube formed with the sieve plate and housing wall; said housing wall and dry gas tube each including coupling means at their opposite ends for joining the unit to a similar one piece modular unit to form an elongated multi-compartment mixing column.
 26. The combination as set forth in claim 25 wherein the tubular housing wall includes a rib and groove construction for snap fitting two or more modular units together.
 27. The combination as set forth in claim 25 wherein the tubular housing wall has an upstanding annular flange adjacent its upper end which flange has an annular beveled wedge surface thereon.
 28. The combination as set forth in claim 25 wherein the tubular housing wall includes a depending annular flange adjacent its lower end with a beveled wedge surface thereon.
 29. The combination as set forth in claim 25 wherein the dry gas tube is integrally formed with the sieve plate and centrally located thereon so as to have a common longitudinal axis with the tUbular housing wall.
 30. The combination as set forth in claim 25 wherein the gas tube includes a coupling member at an upper end, and said coupling member includes an enlarged receiver sleeve with an inwardly tapered upper lip surface, a transverse shoulder surface below said lip surface and an inner wall surface between the lip surface and shoulder surface; and said dry gas tube has a lower coupling portion that includes a tapered end surface adapted to engage the tapered lip surface of a dry gas tube receiving sleeve of an adjacent similar modular unit, whereby the modular units can be coupled to form a continuous dry gas feed line extending through a plurality of modular mixing units.
 31. A method of humidifying a medical gas for direct administration to a patient during inhalation therapy comprising the steps of: forcing pressurized dry medical gas confined axially and downwardly into a lower reservoir portion of a container at least partially filled with a humidifying liquid; restricting the gas axially and directing it progressively upwardly through a series of vertically stacked interconnecting chambers with a portion of the chambers being submerged in said liquid and portion of the chambers extending above the liquid reservoir; progressively increasing the humidity of the gas in each successive vertical chamber forcing the gas through a series of vertically spaced perforated plates while contained in said chambers and maintaining a body of liquid above the perforated plates above the liquid level in the container reservior and progressively forming gas bubbles at each of the perforated plates and passing it through the plates with an increasing gas-liquid interface before it ascends through the liquid above the plates and at a substantially reduced noise level; collecting the gas most highly humidified adjacent the top of the container; and conducting the humidified gas into a feed line adapted to be connected to a patient for breathing.
 32. The method as set forth in claim 31 including progressively directing the gas through at least three humidifying chambers as it proceeds from a lower portion of the container to an upper portion of the container. 